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Highly enhanced foams for stability and decontamination efficiency with a fluorosurfactant, silica nanoparticles, and Ce(IV) in radiological application

Yoon, In-Ho, Kim, Seung Eun, Choi, Mansoo, Kim, Seonbyeong, Choi, Wang-Kyu, Jung, Chong-Hun
Environmental technology & innovation 2020 v.18 pp. 100744
cetyltrimethylammonium bromide, chemical bonding, chromium, cobalt, decontamination, foams, iron, nanoparticles, nitric acid, oxidants, radionuclides, silica, stabilizers, surfactants, wastes
The stability and decontamination efficiency of foams containing a fluorosurfactant, stabilizer, and the chemical reagents with HNO₃ and Ce(IV) for the decontamination of Fe–Cr oxide layers containing ⁶⁰Co radionuclides were tested to find their optimum formulation. The stability of foams containing 2 M HNO₃ and 0.5 M Ce(IV) with 1 wt% silica nanoparticles (NPs) is higher for Zonyl TBS (an anionic fluorosurfactant) than for other surfactants such as SDS (anionic) and CTAB (cationic). This result indicates that Zonyl TBS is more suitable for the harsh conditions required for the use of the oxidant Ce(IV) and silica NPs, indicating that this formulation is conducted for the decontamination test. After three repetitions of the decontamination test, performed by re-injecting air into the decontamination foam, approximately 73% of ⁶⁰Co was removed from the corroded specimen (SUS 304) by the foam containing 1% v/v Zonyl TBS; this removal value is close to that obtained with the chemical decontamination solution alone, i.e., 80%. The results of secondary waste showed that the decontamination foam contains only 70 ml of chemical decontamination solution and 280 ml of injected gas, indicating that decontamination foam decreased the generated secondary waste by 80%, compared to the use of 350 ml chemical decontamination solution. Moreover, the results indicate that the use of silica NPs and the TBS surfactant enhances foam stability, particularly because of the resistance to harsh conditions of the surfactant due to its low pKa and strong C–F bonding.